- #1
kimkibun
- 30
- 1
is it possible to estimate all parameters of an n-observation (X1,...Xn) with same mean, μ, but different variances (σ21,σ22,...,σ2n)? if we assume that σ2i are known for all i in {1,...n}, what is the mle of of μ?
kimkibun said:is it possible to estimate all parameters of an n-observation (X1,...Xn) with same mean, μ, but different variances (σ21,σ22,...,σ2n)? if we assume that σ2i are known for all i in {1,...n}, what is the mle of of μ?
kimkibun said:i forgot to tell you that the n-observations was drawn out from a normal population..well anyway, is it possible that different variances might affect the maximum likelihood of the mean?
Parlyne said:They do. If you go through the maximum likelihood logic with different variances, you'll find that the maximum likelihood estimator for the mean is the standard weighted average:
[tex]\frac{\sum_{i=1}^N w_i x_i}{\sum_{i=1}^N w_i}[/tex]
with
[tex]w_i = \frac{1}{\sigma_i^{\phantom{i}2}}.[/tex]
kimkibun said:can you please show me how you get that?
the mle for μ that i got is this,
(Ʃxi/Ʃσi2)(Ʃ1/σi2)
is it possible to find the mle of the parameter σi2?
The maximum likelihood estimator (MLE) of μ for X1,...Xn with known σ2i is a statistic that estimates the true mean (μ) of a population based on a sample of n independent and identically distributed (i.i.d.) random variables (X1,...Xn) with known variance (σ2i). It is the value of μ that maximizes the likelihood function, which is a measure of how likely the observed data are given a specific value of the parameter μ.
The MLE of μ for X1,...Xn with known σ2i is calculated by taking the derivative of the likelihood function with respect to μ, setting it equal to 0, and solving for μ. This results in the sample mean (X̄) being the MLE of μ, which is an unbiased estimator of μ. The formula for the MLE of μ is: μ^ = X̄ = (X1 + ... + Xn)/n.
The assumptions for using the MLE of μ for X1,...Xn with known σ2i are that the sample of n i.i.d. random variables (X1,...Xn) is representative of the population, and that the population has a normal distribution with known variance (σ2i). If these assumptions are not met, the MLE of μ may not be the best estimator for the population mean.
The known variance (σ2i) affects the MLE of μ for X1,...Xn by providing more information about the population distribution. This allows for a more precise estimate of the population mean, as the likelihood function is more sensitive to changes in μ when the variance is known. However, if the known variance is incorrect or does not accurately represent the population, the MLE of μ may be biased or inaccurate.
No, the MLE of μ for X1,...Xn with known σ2i is specifically designed for continuous data that follows a normal distribution. It may not be appropriate for other types of data, such as categorical or discrete data, as the assumptions for using the MLE may not be met. In these cases, other estimation methods should be used to estimate the population mean.